A reciprocating compressor in the related art adopts a structure comprising a cylinder block having a plurality of cylinders formed therein, pistons that make reciprocal movement inside the cylinders, a front-side cylinder head fixed to one end of the cylinder block via a valve plate, a rear-side cylinder head fixed to the other end of the cylinder block via a valve plate, a front-side delivery chamber formed at the front-side cylinder head, into which a working fluid let out from front-side compression spaces formed on the front side within the cylinders is guided, a rear-side delivery chamber formed at the rear-side cylinder head, into which the working fluid let out from rear-side compression spaces formed on the rear side of the cylinders is guided, a plurality of delivery passages formed at the cylinder block to range substantially parallel to the cylinders and an outlet port located at either the cylinder block or a cylinder head, which communicates between one of the delivery passages and an external circuit, with another delivery passage that does not communicate with the outlet port made to communicate with the front-side delivery chamber and the rear-side delivery chamber and also made to communicate with the delivery passage communicating with the outlet port via a guide passage (see Japanese Unexamined Patent Publication No. H11-117859).
In this structure, the coolant gas delivered into the compression spaces is let out to the external circuit from the outlet port via the delivery passage, which is not in communication with the outlet port, the guide passage and the delivery passage communicating with the outlet port and thus, any stagnation of the coolant gas in the delivery passage, which is not in communication with the outlet port, can be eliminated. This allows both delivery passages to be used as effective mufflers so as to reduce the extent of pulsation.
In addition, since the end of the delivery passage communicating with the outlet port, located on the opposite side from the outlet port side, is closed off, one end of the guide passage is made to open toward the end of the delivery passage communicating with the outlet port, which is located on the opposite side from the outlet port side, so as to ensure that the space at the closed and does not become a refuge for the working fluid and that the volumetric capacity of the space can still be effectively used as a passage for the working fluid in Patent Reference Literature 1 described above.
However, while the extent of pulsation can be reduced to some extent in the reciprocating compressor described above, it has been found to manifest a drastic increase in the level of discharge pulsation over a specific rotational rate range (1200 to 1600 rpm). For this reason, there are limits to the extent to which vibration and noise at the compressor can be reduced.
In addition, in an automotive refrigerating cycle equipped with the compressor described above, the liquid coolant starts to collect inside the compressor when the compressor is left in an OFF state over an extended period of time. In this situation, the internal pressure at the evaporator connected on the intake side of the compressor rises as the temperature inside the cabin increases. Thus, if the path between the intake port and the outlet port inside the compressor is blocked by the liquid coolant, an increase in intake pressure will cause the liquid coolant containing oil inside the compressor to be pushed out and, as this process is repeated, a large quantity of oil ends up being taken out from the compressor. Then, as the compressor without sufficient oil therein is started up, the compressor may, in the worst-case scenario, seize up.
While the relative increase occurs in the extent of discharge pulsation over the specific rotational rate range as described above, the compressor in which the working coolant having been delivered into the front-side delivery chamber and the working coolant having been delivered into the rear-side delivery chamber then flow from the individual delivery chambers along directions opposite from each other through the delivery passage to collide with and join each other at a middle position inside the delivery passage, tends to induce pulsation readily in the first place. For this reason, further measures must be taken to reduce the extent of pulsation of the working fluid having flowed in one direction and the working fluid having flowed in the other direction, joining each other within the delivery passage, in the compressor with this particular delivery path.
A primary object of the present invention, which has been completed by addressing the problems discussed above, is to reduce vibration and noise by reducing the extent of discharge pulsation attributable to the structure of the compressor. Another object of the present invention is to provide a reciprocating compressor with which a reduction in the extent of discharge pulsation and a reduction in the extent to which oil is allowed to flow out can both be achieved.